The present invention generally relates to power hand tools and more particularly to circular saws.
Power hand tools such as circular saws have been commonly known for decades and generally have a foot plate that slides on a work piece that is being cut, a circular saw blade that may have a diameter as small as a few inches or as large as seven or more inches, with the saw blade extending through an opening generally perpendicular to the plane of the foot. The saw is typically driven by an electric motor that is powered by either an AC or DC power source, the DC power source often being a battery pack or the like.
Circular saws are commonly used on construction sites to saw boards that are used in framing a building or for cutting large plywood or other material sheets into smaller pieces, all of which are known to those skilled in the power hand tool art. Such circular saws have been the subject of much research and development and significant improvements have been made in their design and construction over the many decades that they have been used.
Significant developments have included improved blade guards, both above and below the blade for protecting a user from injury, with the lower blade guards being designed to be moved out of the way when a board or the like is to be cut. Ergonomic developments have been made so that user handles, including main handles or auxiliary handles, facilitate the easy cutting of a sheet or board along a desired path. The early circular saws were designed to only make perpendicular cuts relative to the work piece, but later developments included an adjustable bevel angle capability.
Even with the many improvements that have been made in the design of circular saws, a common problem that continues to exist is the accumulation of sawdust and/or other debris on the line of cut which hinders the user from following the desired cut line to produce a straight and accurate cut. Improvements in motors that are used in circular saws and other hand tools have resulted in the motors being smaller in size relative to the power that they develop. Because cutting of some materials, particularly those which are relatively thick, put a significant load on the motor, it is necessary to have an adequate flow of air near the motor to dissipate heat during operation. Because of this requirement, many motors have an internal fan blade driven by the motor to expel air from the motor enclosure or housing for the purpose of cooling the motor. The air has been expelled through openings that have been positioned at many different locations in circular saws of the prior art.
While the circular saw designs are sufficient to expel the air and dissipate heat during operation, little regard has heretofore been made in directing the air in any particular direction or for any apparent purpose other than to expel the air from inside the motor housing.